The present invention relates to a releasable substrate on a carrier and a method and system for providing such.
Flexible displays represent an upcoming trend in next-generation display technology. A flexible display may comprise a flexible substrate with electronics such as thin film transistors (TFT) or other components manufactured thereon. Manufacturing of electronics, in particular integrated circuitry, may comprise harsh processing conditions, e.g. exposure to radiation and/or vacuum in a lithographic step, and/or exposure to high temperatures, e.g. during baking steps. A problem encountered during manufacturing of electronics directly on a flexible substrate may be a low dimensional and/or thermal stability of the substrate. This may result e.g. in alignment issues during lithographic exposure. One solution for improving the stability of a substrate may be adhering the substrate to a carrier during manufacturing.
On the one hand adhesion between the substrate and carrier should be strong enough to withstand the various processing conditions encountered during manufacturing, e.g. high temperature, vacuum, UV radiation, and rapid acceleration. On the other hand the adhesion should not prevent release of the substrate from the carrier after manufacturing without damaging the electronics. It can be challenge to find a compromise between these two criteria.
As a first solution, WO2011/151457 discloses a technique comprising: securing a device substrate to a carrier using one or more adhesive elements; forming electronic elements on the device substrate with the device substrate thus secured to the carrier; and thereafter reducing the adhesion strength of at least one of the one or more adhesive elements to facilitate the release of the substrate from the carrier. The reduction in adhesion strength is triggered by a threshold temperature. Unfortunately, such adhesive elements may not be suitable for withstanding high temperatures (>200° C.) or other harsh processing conditions encountered during manufacturing.
As another solution, US 2012/0201961 discloses a method for fabricating a substrate structure applied in flexible electrical devices comprising providing a carrier, forming a release layer on the carrier with a first area and forming a flexible substrate on the release layer and the carrier with a second area, wherein the second area is larger than the first area and the flexible substrate has a greater adhesion force than that of the release layer to the carrier. The release layer with greater adhesion force can be separated from the carrier by cutting along the two ends of the release layer with lower adhesion force. Unfortunately, this method relies on the foil being solution processed and able to adhere to the carrier. Also, this method may be unsuitable for large substrates.
There is a need for a releasable substrate on a carrier that is able to withstand harsh processing conditions encountered during manufacturing yet can be easily removed after processing. There is a further need for being able to process a wider variety of substrates. Correspondingly there is a need for method of providing said releasable substrate on a carrier and a system for implementing said method.